The formation of central galaxies in FGs is thought to be the end result of the group evolution [1]}, [2]}. The main actor, in this scenario, would be dynamical friction. However, [3]} suggested that the main difference between FGs and non-FGs has to be found in the initial velocity distribution. In particular, he found that satellite galaxies in FGs should be located on more radial orbits than in non-FGs. This would favour low angular momentum mergers, for which dynamical friction could be more effective [4]}.
